278 Professor E. A. Schdfer on the Paths of Volition, [March 20, 



motor-cells of the cord and lower level centres. One must, therefore, 

 admit the possibility that the paralysis which results from section 

 of the antero-lateral descending fibres, may be at least in some measure 

 connected with this diminution of tone of the motor apparatus of the 

 cord ; and one of the questions which we have to consider is whether 

 this by itself is a sufficient explanation of the resulting paralysis. 

 The question is not an easy one to answer, but it may be stated that 

 the paralysis which is produced by severance of the antero-lateral 

 descending fibres, is at first so complete that nervous impulses which 

 are produced by direct electrical excitation of the cerebral cortex are 

 unable to affect the motor apparatus of the cord, whereas in Mott and 

 Sherrington's experiment excitation of the cortex produced the usual 

 contractions of the voluntary muscles. It seems, therefore, probable 

 that the fibres of the antero-lateral descending tract do serve to 

 convey impulses from the volitional centres of the brain to the 

 grey matter of the cord (even although we admit that by way of 

 the vestibular nerve and the nucleus of Deiters, and by way of the 

 optic nerve and the corpora quadrigemina, impulses may also pass 

 along those fibres to assist in maintaining the tone of the motor 

 centres), and thus furnish a path for volitional impulses other than 

 that furnished by the pyramidal tracts ; a path which in all vertebrates 

 below mammals is sufficient for the entire conduction of volitional 

 impulses from the cortex of the brain to the motor apparatus of the 

 cord. 



[E. A. S.] 



